A tall, dishevelled guy with a mountainous Afro starts beatboxing. Using an effects pedal, he loops the rhythm, adds a vocal bassline and loops that too. Over the top, he sings this sweet refrain: "Shit, motherfucker, ass, tits, cunt, cock/ Come on!" It's as good an entry point as any to the world of Reggie Watts: a hip-hop influenced musical comic whose work is unlike any you'll have seen before.

In the USA, Watts is at the forefront of an exciting raft of alternative talent. In New York and LA in particular, there's a vibrant leftfield comedy scene, full of performers who spend more time making weird online videos in their backyards than trying to break into Hollywood. It involves comics UK crowds are already familiar with, such as Flight Of The Conchords stars Kristen Schaal and Eugene Mirman, as well as talents that aren't on our radar yet like Rory Scovel, Jon Dore and Natasha Leggero.

As a guy who spent much of his childhood in Great Falls, Montana watching British TV (from Fawlty Towers to Poirot), Watts's semi-regular visits to London have seen him acquire a cult following here. That said, he had a few concerns prior to his first UK appearance in 2004. While his usual voice is a slow Midwestern mumble, on stage Watts speaks in an extraordinarily accurate English accent for, he says, "a quarter to a half of the time. It's just something I enjoy doing. I was nervous about how people would react here but fortunately people were like, 'Oh yeah, you must be from London.'"

The roots of Watts's uncanny vocal abilities – from pitch-perfect impressions to the aforementioned beatboxing – goes backto his childhood. "It comes from growing up in a bilingual household. My mother's French, so I grew up with two languages. I just loved mimicking sounds. Whenever I'd see something on TV like someone [dead-on cockney accent] 'Why's he doing that?' I'd want to try it."

The need for constant experimentation is what makes Reggie Watts so special. You never get the sense – as with many musical comics – that you're watching well-honed set-pieces. Instead, he develops most of his songs spontaneously, a feat of improvisational skill that means that you can never be entirely sure what's coming next. Watts says that 95%of his show is usually improvised, and that he tries to go by the responses of the audience. "There's a real-time reaction to what's happening. I'm not the kind of guy who goes [posh English accent] 'You there sir, what do you think?' I can't really do that. So my version of interacting is listening to how the audience is responding. And if the audience are laughing, I may go on to a different tack." It means that every Reggie Watts show is unique: "Every performance is an opportunity to have something new or to learn something new. Not necessarily, but hopefully."

Such commitment to free creativity is not without risks. There are times when Watts's rude songs, rants and disconnected musings sail straight over the audience's heads. "I've done corporate gigs for companies like Fortune Magazine, and sometimes people are just like … 'Uh, what is happening now?' It would be different if I could go up there, grab the mic and go, 'So, what's the deal with…' but I never do that. Instead there's just this strange-looking man up there just going off on tangent after tangent. Usually I'd say, at least 70% of the audience are laughing all the time. But there will be people with whom I just make no connection at all. They don't know why they're there."

'I like the idea of just ambiently being around the mainstream … I'm pretty lazy when it comes to creativity'

Reggie Watts. Photograph: Anthony Pidgeon/Redferns

Once you get past the hair and strange stage presentation, the content of Watts's show is fascinatingly eclectic. There are moments of great beauty, both musically and verbally, as he sings about romance or thinks fondly about childhood memories. But these moments can suddenly give way to violence, as he starts raging against reality TV or outlining ways to commit murder. He certainly keeps you on your toes. "I love the idea of something beautiful happening, and then it being abrasively cut into," he says. "Because in a way it's similar to switching channels or surfing the web; I like people getting lulled into something and then taking them somewhere else. I'm doing the kind of show that I would want to see. Sometimes I do things that I know will piss off people. But I always turn it around in the end and give them something …hopefully delightful."

The range of Watts's ideas are matched by an equally diverse CV. In his time, he's worked with everyone from anti-corporate pranksters The Yes Men ("they're intense, strange guys with a huge amount of belief"), to US stand-up and Gervais chum Louis CK ("he's definitely a genius but not necessarily the friendliest guy"), plus a spell opening up for Conan O'Brien on his post-Tonight tour, which Watts describes as like going on the road with the Stones, though presumably only in terms of scale. But if you can't experience Watts in person, you can soak up some of his magic on his excellent audio release Why Shit So Crazy?, which covers all bases of his unorthodox approach. Just don't expect to see him in his own TV series yet. While he is making a "fake surrealist talkshow" for US indie channel IFC, beyond that, he says, "TV's not my thing. I don't care about all the bullshit, I just want to make a funny idea, that's all.

Wherever his career takes him, he's adamant that it has to involve a) no compromises and b) not too much hard work. "I like the idea of just ambiently being around the mainstream, as opposed to [big booming voice] 'The Reggie Watts Show!' It's a lot of pressure, and I don't want pressure. I'm pretty lazy when it comes to creativity. I just want it to be easy and fun."